1. Technical Field
This invention relates to the field of sheet metal assembly, and more particularly to apparatus for the joining of metal sides of a housing for electrical appliances such as a computer output printer.
2. Description of the Prior Art
In printing devices such as computer output printers, typewriters or tele-typewriters, a printing carriage is generally moved along a record carrier by an electrical drive mechanism. The typing carriage is mounted on guide rails which, in turn, are disposed in a printer support a in non-twisting and shape-stable manner. The printer support is often of boxshaped design and composed of individual sheet metal elements produced by stamping.
To interconnect or join the sheet metal elements, it is known in printing devices and other mechanical precision equipment subjected to severe stresses due to vibrations, to weld or screw the sheet metal elements together. But these joining methods are expensive and are used only when extreme stresses are involved. The also possible, cheaper methods, namely to peen over or to joggle the sheet metal elements have the disadvantage that the form closure at the joints is not perfect so that a loose connection may occur. The above-described joining methods, except the use of sheet metal screws, have the further disadvantage that after assembling or joining the sheet metal elements together, their disassembly, as may be required for servicing, is difficult or even impossible.
Another problem when joining sheet metal elements which serve as housing parts for printing devices or other electrical appliances is electromagnetic incompatability. Since the housing elements of such apparatus generally carry ground potential for safety reasons, it must be insured that the sheet metal elements are well connected to each other electrically.